Alkoxystyrenes such as p-methoxystyrene (PMOS) may be polymerized by free radical, cationic or anionic methods, but each of the known methods has drawbacks. Further, very high molecular weight polymers can not be produced by the known methods.
Anionic polymerization of alkoxystyrenes are subject to termination reactions, and generally result in only oligomers, or at best, low molecular weight polymers.
Free radical polymerization of alkoxystyrenes are subject to the typical free radical termination reactions of combination and disproportionation.
Cationic polymerization of alkoxystyrene can be performed utilizing a iodide ion containing initiator with a coinitiator of a divalent metal iodide or as described by Higashmimura et al. in "Living Cationic Polymerization of p-methylstyrene by Hydrogen Iodide/Zinc Iodide at Room Temperature," Polymer Bulletin, 19, 7-11 (1988). Living polymers are produced. But the preferred zinc iodide coinitiators are toxic and difficult to separate from the polymer. If the zinc iodide is not removed from the polymer, it imparts an unacceptable color.
Each of these known processes involve utilization of initiators which are soluble in the polymerization mediums. Process steps are required to remove the initiators and these process steps are typically energy intensive.
The objects of this invention are therefore to provide a process to polymerize alkoxystyrenes polymers, the process utilizing a heterogeneous and non-toxic initiator system. It is a further object of this invention to provide a high molecular weight polymer comprising alkoxystyrene monomer units, the polymer having a broad molecular weight distribution.